Alcoholism is a consequence of prolonged ethanol abuse and has been associated with the aging of cognition and psychomotor function. Because alcoholics go through repeated rounds of ethanol withdrawal (EW), we propose using repeated EW to investigate whether aging with exacerbates the effects of EW on cognition and psychomotor function through oxidative insults to mitochondria. We also propose to investigate whether a loss of estrogen contributes to this problem. This work may have particular significance for female alcoholics, who simultaneously undergo EW and estrogen deficiency in their advanced age. Our pilot study has demonstrated that estrogen protects against EW toxicity in both young and old female rats. In the proposed study, we will use three age groups of ovary-intact female rats: 5 months old, 12 months old, and 16 months old, when the ethanol diet begins. We propose to use a diet cycle of 25 days of ethanol followed by 5 days of withdrawal repeated for 5 cycles. These cycles will be timed such that rats will be at the estrus phase (high estrogen levels) when diet is removed and EW signs peak. In Aim 1, we will determine the effects of EW on cognition and psychomotor functions during aging. Rats at the estrus phase will be withdrawn from an intermittent ethanol diet and tested for psychomotor function using established behavioral methods. In Aim 2, we will characterize the mitochondrial oxidative mechanisms underlying the deleterious interaction between age and EW. We will measure oxidative markers (reactive oxygen species, lipid peroxidation) and consequent mitochondrial dysfunction (collapse of mitochondrial membrane potential and ATP loss). In Aim 3, we will characterize oxidatively modified mitochondrial enzyme cytochrome c oxidase (COX) which we hypothesize mediates the deleterious interaction between age and EW. We will quantify carbonylation of COX and lipid-peroxide-modified COX using liquid chromatography-mass spectrometry and tandem mass spectrometry. In Aim 4, we will determine whether estrogen deficiency during aging contributes to EW-induced oxidative damage to mitochondria and psychomotor deficit. The same psychomotor and oxidative markers will be measured in ovary-intact and ovariectomized rats with or without estrogen replacement. These studies may ultimately contribute to a better understanding of and strategy for female alcoholics undergoing EW during brain aging.